# 數組 [![badge](https://img.shields.io/endpoint.svg?url=https%3A%2F%2Fgezf7g7pd5.execute-api.ap-northeast-1.amazonaws.com%2Fdefault%2Fsource_up_to_date%3Fowner%3Derg-lang%26repos%3Derg%26ref%3Dmain%26path%3Ddoc/EN/syntax/10_array.md%26commit_hash%3D603abbd5fa3f8baffe0d614758e1a554705e6732)](https://gezf7g7pd5.execute-api.ap-northeast-1.amazonaws.com/default/source_up_to_date?owner=erg-lang&repos=erg&ref=main&path=doc/EN/syntax/10_array.md&commit_hash=603abbd5fa3f8baffe0d614758e1a554705e6732) 數組是最基本的__collection(聚合)__ 集合是一個可以在其中包含多個對象的對象 ```python a = [1, 2, 3] a: [Int; 3] # 類型說明: 分號后的數字為元素個數 # 如果元素個數未知，可以省略 a: [Int] mut_a = [!1, !2, !3] mut_a[0].inc!() assert mut_a == [2, 2, 3] ``` 通常，數組不能包含不同類型的對象 ```python. [1, "a"] # 類型錯誤: 第一個元素是 Int，但第二個元素是 Str ``` 但是，您可以通過像這樣顯式指定類型來繞過限制 ```python,compile_fail [1: Int or Str, "a"] ``` ## 切片一個數組也可以同時取出多個值。這稱為切片 ```python l = [1, 2, 3, 4] # 與 Python 中的 l[1:3] 相同 assert l[1.. <3] == [2, 3] assert l[1..2] == [2, 3] # 與 l[1] 相同 assert l[1..1] == [2] # 與 Python 中的 l[::2] 相同 assert l[..].step(2) == [2, 4] ``` 通過切片獲得的對象是數組的(不可變的)副本 ```python print! Typeof l[1..2] # [Int; 4] ```